Air conditioning system



Dec. 10, 1940. F. w. BORSE ETAL 2,224,629

AIR CONDITIONING SYSTEM Filed April 9, 1938 3 t FellnxWBorse "W" ifhurlles Rdfilfimr's' Patented Dec. 10, .1940

UNITED STATES PATENT OFFICE AIR CONDITIONING SYSTEM Application April 9, 1938, Serial No. 201,160

5 Claims.

This invention relatesto an air conditioning system and more particularly to a cooling and denumidifying system.

In accordance with our invention, the temperature and humidity of a space is controlled by passing air being circulated thereto over a coil or coils through which a suitable cooling medium is circulated, the amount of dehumidification and sensible cooling that is efiected being controlled 10 by controlling the rate of how of the cooling medium through the coil. The flow of the cooling medium is so controlled that when there is a call for maximum sensible cooling only, the rate of flow through the coil may be less than when 15 there is a call for maximum dehumidification only. In other words, while the rate of flow is controlled both in accordance with the demand for sensible cooling and the demand for dehumidification, an increase in the demand for dehug midification may cause a greater increase in the rate of flow. than a like increase in demand for sensible cooling. 'Since a onsiderably great-t er amount of heat must be removed from the air to effect dehumidification thereof than to effect 25 sensible cooling, by properly proportioning the rates of flow in accordance with the above, it is possible to more effectively control the temperature and humidity of the air than is possible where the temperature and humidity responsive 30 devices exercise the same influence on the flow controlling means.

It, is therefore an object of our invention to provide a novel control means for a coil through which a cooling medium is circulated to cool and dehumidify the air being circulated through a space whose temperature and humidity. is to be controlled.

Other objects and advantages will become apparent upon a study of the specification, claims,

40 and appended drawing, the single figure of which is a schematic view of an air conditioning system embodying the principles of our invention.

Referring now to the drawing, an air conditioning chamber is represented by the reference 5 character I0, this chamber being provided with a fresh air inlet H ,and a return air inlet l2.

Dampers l3 and I4 positioned in the fresh and return air inlets, respectively, may.be provided for controlling the proportions of fresh and re- 50 turn air admitted to the chamber to and may be several different paths.

Located within the chamber I0 are suitable cooling coils 20 through which a cooling medium is circulated by means of a pump 2|. A cooling tank 22 is provided for cooling the water or other cooling medium and this tank is illustrated as 5 being cooled by an' evaporator 23 of a refrigeration system. This refrigeration system may include a compressor 24, a condenser 25, and an expansion valve 26, these elements being connected together and operating in the manner well known in the art. The operation oil compressor 24 may be controlled by a mercury switch 28 mounted on a lever 29, this lever being biased by means of a spring 30 into engagement with a bellows 3|. Bellows 3| is connected by means of a capillary tube 32 with a bulb 33 located within the cooling' tank 22, this tube, bulb, and bellows being provided with a suitable volatile fill whereby the bellows expands and contracts in response to variations in temperature of the water in the tank 22. Switch 28 controls the current to the compressor a motor from lines 8, 9 connected to a suitable source of power (not shown), current flowing from line 8 through wire 2!, switch 28, wire 39, motor 24, and wire 44 to line 9, and when the temperature of the fluid in the tank 22 drops to a predetermined value, the bellows 3| will contract and cause the switch 28 to be tilted in the opposite direction from that shown thus interrupting the current to the compressor motor and stopping theoperation of the refrigeration system.

The fluid circulated by the pump 2| may follow A pipe 35 connects the pipe 36, leading. to the inlet of the cooling coil 35 20, to a pipe 31 which is connected to the outlet of the coil 20; The flow of water through the bypass 35 and the pipe 31 is controlled by a threeway mixing valve 38 whereby the proportion of water flowing through the by-pass 35 and through the pipe 31 from the coil 20 depends upon the position of the valve 33. A .pipe 43 is connected to the pipe 31 and forms a by-pass around the valve 33, the

flow ofwater through this pipe being controlled 45 by a three-way mixing valve 4 l with the threeway valve 33 in a position to prevent flow of.water through the pipe 31, water may still be permitted to flowthrough the coil 20 if the three-way valve ll is in proper position, the amount of waso ter which is permitted to flow through, the coil depending upon the position of this valve member. A hand operated valve 42 is provided in'the pipe 31 to control the maximum amount of water that may flow through the coil 20 when the i inlet from pipe 48 to the three-way valve 4| is entirely closed and when the inlet from the pipe 31 to the three-way valve 38 is entirely open, or in other words, to control the maximum flow of water through pipe 31. A second manually operated valve 45 may be positioned in the pipe 85 to control the amount of water that may flow through the pipe 35 and the three-way valve 88 for any position 01' the valve 38. A check valve 48 is "provided in the pipe 31 to prevent flow of water through the pipes 38, 85, valve 38, and pipe 31 to the outlet of the coil 28.

The position of the three-way valve 4| may be controlled by a motor 58 having an arm connected by means of a link 52 to the valve stem 53. This motor may be a proportioning motor of the type illustrated in Patent 2,028,110 issued to D. G. Taylor on Jan. 14, 1936, and controlled by humidity responsive device 55 mounted in the space 8, this device including a humidity responsive element 58 connected to a lever 51 pivoted at 58. A spring 59 is connected to the left end 01' the lever 51 and biases the opposite end of the lever in a downward direction. A resistance 88 is provided over which the right end of the lever 51 moves in response to variations in humidity in the space l8. Upon an increase in humidity in the space the humidity responsive element 58 will become elongated and the lever 51 will move downwardly over the resistance 88 under the influence of the biasing spring 59. Upon a decrease in relative humidity in the space, the humidity responsive element 58 will contract thus causing the lever 51 to move upwardly over the resistance 88. The position of the lever 51 with respect to the resistance 88 controls the position of arm 5| driven by motor 58 as will be apparent upon a study of the aforementioned patent. As the humidity in the space rises 'the motor operates to move the arm 5| in a direction to cause an increased flow of cooling fluid through the pipe 48 and a decreased flow through, the pipe 48 and when the humidity reaches a predetermined high value there will be no flow through the pipe 48 and a maximum flow through the pipe 48. As the humidity drops to a predetermined low value the valve will be operated to close the inlet from pipe 43 so that no water flows through this pipe andthe flowthrough pipe 48 will be at a maximum.

A motor 85 similar to the motor 58 is provided for controlling the position of the threeway valve 38. An arm 88 driven by this motor is connected by means of a link 81 with the valve stem 88. This motor may be controlled by a device 18 responsive to the temperature of the air in the space l8. Temperature responsive device 18 may include a bimetallic element 1| carrying an arm 12 which sweeps over a resistance 13 in response to temperature changes in the space I 8 whereby the position of arm 88 driven by motor 85 is controlled in accordance with the temperature in the space. The operation of motor 85 may be compensated by the outdoor temperature so that as the temperature of the air outside of the building rises, a higher temperature will be maintained in the space l8 in order to secure proper temperature conditions within the space. For this purpose a controller 88 is provided, this controller including a bellows 8| connected by means of a capillary tube 82 to a bulb 83 which may be located in the fresh air inlet ll of the chamber l8. This tube, bulb, and bellows may be provided with a sui expansion of the bellows 8| and this arm moves in the reverse direction in response to a drop in outdoor temperature. The left end of this resistance is connected by means of conductors 95 and 9| to the terminal 92 of the motor 85. The opposite end of the resistance 81 is connected by means of conductors 98 and 98. to the terminal 94 of the motor 85. The arm 88 of lever 85 is connected by means-of conductors 98, resistance 99, and conductors I88 and |8| to the terminal 98. .As the arm 88 moves to the right in response to an increase in outdoor temperature the valve 88 is operated by motor 85 to reduce the flow of water through the pipe 31 and accordingly through the coil 28 by way of this valve. 12 of thermostat 18 moves toward the right end of resistance 13 in accordance with a rise in the temperature in the space l8 and this side of the resistance is connected by means of conductors |821 and 9| to the motor terminal 92. .The opposite end of the resistance towards which the arm 12 moves in response to a temperature drop in the space is connected by means of conductors I83 and 98 to the motor terminal 94. The arm 12 is connected by means of the center tapped resistance I85 and conductors I88 and IN to the motor terminal 93. It will now be noted that by reason of the relative arrangements of the resistances 13 and.81 that if movement of arm 88 to the right in response to an increase in outdoor temperature causes movement of arm 88 by the motor 85 in a direction to causea decrease in flow the motor 85 will be operated in the opposite direction and will accordingly cause an increase in the flow of water through the pipe 81. By reason of the resistance 99 in the circuit to the arm 88 this arm will have less effect on the operation of motor 85 for agiven range of movement thereof than will the arm 12. In other words, for a movement of arm 12 through the range indicated by D the motor 85 may be operated from one extreme position to the other whereas in order to give the same movement to the motor the arm 88 must operate from one end to the other of resistance 81. Thus the effectof a change in outdoor temperature is to shift the control range of the arm 12 so as to maintain a different temperature in the space as the outdoor temperature varies. The center tapped resistance I85 serves to maintain the length of the operating range of arm 12 the same at all times regardless of the location of this operating range as determined by the controller 88.

When the temperature in the space is at a predetermined low value the thermostat 18 will cause motor 65 to position the three way valve 38 so as to close this valve to pipe 31 and open it to the by-pass pipe 35. If the relative humidity is low, the humidity controller will cause the motor 50 to position valve 4| so that this valve closes completely to pipe 43 and opens wide to pipe 48. Thus, when both space temperature and relative humidity are low, the

5 valves 38 and 4| will be positioned for preventing flow of cooling fluid through pipe 31 and pipe 43. This will prevent any flow of cooling fluid through the cooling coil 20. At this time, it will be noted that valve 38 is wide open to by-pass pipe 35 and valve 4| is wide open to pipe 48. The pump 2| will therefore circulate cooling fluid from the cooling tank 22 through pipe 36, pipe 35, valve 38, pipe 48, valve 4|, and the return pipe back to cooling tank 22. Therefore, when no cooling fluid is allowed to circulate through the cooling coil 20, this cooling fluid is permitted to circulate through the bypass pipes. This arrangement has the advantage of avoiding churning by the pump 2| when the flow through the cooling coil is prevented. This arrangement also permits circulation of the cooling fluid across the heat exchange surface in cooling tank 22. This circulation prevents stratification of the fluid in cooling tank 22 and thus insures that the cooling fluid stored in this tank will be of maximum effectiveness when required for use.

Assume now that the space temperature is still low but that the relative humidity rises to a value requiring dehumidiflcation. Under these conditions, the three way valve 38 will remain positioned for preventing flow through pipe 31 and directly connecting pipes. 35 and 48. Due to the rise in relative humidity, the motor 58 will position valve 4| so as to permit flow of cooling fluid through pipe 43. Consequently, cooling fluid circulated by'the pump 2| will divide into two branches, one branch passing through the pipes 35 and 48 back to cooling tank 22 and the 40 other branch passing through the cooling coil 20, pipe 43 and valve 4| backto the cooling tank 22. It will be apparent that as the relative humidity continues to rise, the controller 55 will cause motor 50 to position valve 4| for gradually 45 increasing the flow of cooling fluid through the coil 20 and decreasing the flow through the bypass pipes 35 and 48. When the relative humidity rises to a maximum value, the valve 4| will be positioned for opening wide to pipe 43 and closing completely to pipe 48. At this time, the flow of cooling medium through coil 20 will be at a maximum.

Assume now that the relative humidity is at a low value wherein dehumidiflcation is not required but that the space temperature rises toa value requiring cooling. At this time, due to the relative humidity being low the valve 4| will be positioned so as to close completely to pipe 43 and open completely to the pipe 48. As the space temperature rises, the thermostat 10 will cause the motor to position valve 38 so as to permit flow of cooling fluid from pipe 31 to pipe 48, this cooling fluid joining the cooling fluid passing through the by-pass pipe 35. This 5 opening of valve 38 to the pipe 31 and closin of this valve to the by-pass pipe 35 causes cooling fluid to now flow through the cooling coil 28. It will be apparent that when the space temperature rises to a predetermined maximum value, the thermostat 10 will cause motor 65 to position valve 38 to close this valve completely to pipe 35 and open it wide to pipe 31. At this time, the flow of cooling medium under the demand of the thermostat 10 will be at a maximum. As pointed out previously, the valve 42 serves to restrict the flow of fluid through the pipe 28 under the control of valve 38. Preferably this valve 42 is adjusted so that when the valve 38 is positioned for supplying the maximum flow of cooling fluid, this maximum flow will amount to only 40 per cent of the maximumflow which can be caused by the valve 4| which is controlled by the humid ity controller 55. In other words, valve 42 is adjusted so that when the valve 4| is positioned to prevent flow of cooling medium through coil 20, the maximum flow through this coil which can be caused by valve 38 is only 40 per cent of the flow which can be caused by valve 4|. By this arrangement, the humidity controller is able to increase the flow of cooling fluid to a maximum when necessary for dehumidiflcation, while the flow that can be caused by the thermostat is considerably less. This arrangement is highly desirable for the reason that it is necessary to maintain the over all coil temperature considerably lower in order to obtain dehumidiflcation than is necessary in order to obtain sensible cooling. By limiting the effect of the thermostat in this manner, this thermostat is prevented from lowering the coil temperature to a value which would perform too much dehumidiflcation.

While for convenience in description the operation of the temperature control mechanism and the humidity control mechanism have been described separately, itwill be obvious that when both sensible cooling and dehumidification are required at the same time, the two sets of controls will cooperate to provide a resultant flow of cooling fluid through the cooling coil 20 which is proper for obtaining the desired sensible cooling and dehumidifying eifects.

It should be noted that in the arrangement described, the valve 38 controlled by the thermostat 10 handles considerably less cooling fluid than ismequired to be handled by the valve 4|. This valve 38 for this reason may be made considerably smaller than the valve 4|.

By reason of the fact that only enough fluid as is required for dehumidiflcation and cooling is circulated through the coil 28 and the rest of the fluid is by-passed through pipe 35, the cooling requirements of the evaporator 23 in the tank 22 are kept at a minimum for any given condition and the compressor 24 will be operated only long enough and often enough to maintain a predetermined temperature of the water in tank 22.

It will thus be seen that we have devised a very simple and efiective system for controlling the cooling coil to effectively maintain proper conditions of temperature and humidity within a space, compensating the temperature in accordance with outdoor temperature with the use of a single cooling coil and with the provision of a minimum number of parts.

Having described a preferred form of our invention, many modifications may become apparent to those skilled in the art and it should be understood that our invention is limited only by the scope of the appended claims.

We claim as our invention:

1. In an air conditioning system, a cooling coil, means for circulating a cooling fluid through said coil, a by-pass connected between the inlet and outlet of said coil, a three-way valve connected to the outlet of said coil and controlling the relative flows through said coil and said by-pass, a second by-pass around said valve connected to the outlet of said coil and the outlet of said valve, a second three-way valve for controlling the relative flows three-way valve.

2. In an air conditioning system, a cooling coil for removing heat from the air in a space, pump means for circulating a cooling fluid through said cooling coil, a by-pass for permitting flow of fluid by said pump means without flowing through said coil, valve means controlling the relative flows of fluid through said coil and said by-pass, means responsive tothe space temperature in control of said valve means, a second by-pass for permitting a flow of fluid through said coiland around said valve means, a second valve "means controlling the relative flows of fluid through said coil and through said first valve means, and means responsive to the humidity of the space in control of said second valve means.

3. In an air conditioning system, a cooling coil for removing heat from the air in a space, pump means for circulating a cooling fluid through said cooling coil, a by-pass for permitting flow of fluid by said pump means without flowing through said coil, valve means controlling the relative flows of fluid through said coil and said by-pass, means responsive to the space temperature in control of said valve means, a second by-pass permitting a flow of fluid through said coil and around said valve means, a second valve means controlling the relative flows of fluid through said coil and through said first valve means, and means responsive to the humidity of the space in control of said second valve means, said first valve means being incapable of passing as large a flow of cooling fluid through said coil as can be passed by said second valve means.

4. In an air conditioning system, a cooling coil for removing heat from the air in a space, pump means for circulating a cooling fluid through the cooling coil, 8. by-pass for permitting flow of fluid by said pump means without flowing through the coil, first valve means for controlling the relative flows of fluid through said coil and said by-pass a. second by-pass for permitting a flow of fluid through the coil and around said first valve means, a second valve means controlling the relative flows of fluid through said coil and through said first valve means, temperature responsive means, humidity responsive means, one of said responsive means controlling said first valve means and the other of said responsive means controlling said second valve means.

5. In an air conditioning system, a cooling coil for removing heat from the air in a space, pump means for circulating a cooling fluid through the cooling coil, a by-pass for permitting flow of fluid by said pump means without flowing through the coil, first valve means for controlling the relative flows of fluid through said coil and said by-pass, a second by-pass for permitting a flow of fluid through the coil and around said first valve means, a second valve means controlling the relative flows of fluid through said coil and through said first valve means, temperature responsive means, humidity responsive means, one of said responsive means controlling said first valve means and the other of said responsive means controlling said second valve means, the valve means a controlled by the temperature responsive means being incapable of passing as large a flow of cooling fluid through the coil as can be passed by the valve means controlled by the humidity responsive means.

' FELIX W. BORSE.

CHARLES R. HIERS. 

